Over at the Facebook page for The Barefoot Book, author Daniel Howell asks:
Is there a connection between shoes & immunity? Many long-time barefooters report stronger immune systems.
I’d be very careful generalizing. This is one area in which confirmation bias could be very, very strong, and an area in which one should be suspicious of anecdotes. I think a careful study with decent controls would really be needed to tease out any effect.
Let me go into more detail here.
First of all, what is confirmation bias? It is the tendency for humans to remember things that agree with what they already think and to forget those that disagree. This effect has been well-demonstrated in many cognitive studies. So, what we need to do is conduct well-designed studies that remove such bias.
Quite a few barefooters report fewer colds since they started going barefoot. Could that be from a barefoot-induced improved immune system? Well, I suppose it’s possible, but I personally tend to doubt it.
I’ve noticed that I tend to get fewer colds since going barefoot. But let me note how confirmation bias and other confounding factors could work into that. First, I have not kept careful track of my colds over the past years, so I really don’t know if I am getting fewer of them now. It may seem that way to me, but without accurate records, that could just be confirmation bias. Second, my kids are older now and have (mostly) left the house. When they were really little, it seems they were always bringing a cold home, and of course I’d catch it. As they grew older, they didn’t need such close care, and were much more careful about covering their noses when they sneezed, so transmission vectors were reduced. And now with them mostly out of the house, the opportunity for catching something from them is really, really reduced.
Now, that period coincides with my taking up barefooting. Without decent controls, it would be easy to attribute fewer colds to barefooting instead of what is the more likely explanation: fewer chances to get a cold.
There is also the question of mechanism. How might going barefooting increase the efficacy of the immune system when it comes to colds? Without at least a scientifically plausible mechanism, it all seems unlikely. I can think of two possible mechanisms, both fairly weak. First, we’ve noted that going barefoot can improve circulation. Maybe that does something, but the circulation is really only in the feet, and I don’t see how a cold virus would notice that, or how that would effectively raise the immune system. Second, and this one is more plausible, stress has been shown to depress the immune system. So if going barefoot gives you a better feeling of contentment and reduces stress, then it could improve your immune system. I’m not sure this is a really strong effect, though.
So, this is why I say it would really take a decent study to figure it all out.
So far I’ve focused only on colds. There are other areas in which I think barefooting might have a larger impact on the immune system. One reason may be the Hygiene Hypothesis, which suggests that an overly clean environment, one that our ancestors did not have, might insufficiently stimulate the immune system and lead to allergies. Of course, if you go barefoot, your body is physically exposed to a lot of dirt, so it could help with allergies.
I can see another way the immune system could be strengthened. For all the hiking I do, I do occasionally get small dings on my foot, and those dings come into direct contact with the soil and soil micro-organisms. Of course, my immune system has to react to that. What I seem to have noticed is that (look out for confirmation bias!) while originally I would get some redness as my immune system had to develop new antibodies, the more I barefooted, the less redness would result, presumably because my body could call upon my pre-existing antibodies against those soil bacteria. That could come in handy if my body gets exposed to such bacteria in other contexts, and might give me an immunological advantage over a person who had not had such previous exposure.
Bottom line: there is some possible anecdotal evidence, but it needs to be backed up with carefully designed studies.